require('./bootstrap');


//首页背景
let canvas = document.getElementById("canvas");
let ctx = canvas.getContext("2d");
resize();
window.onresize = resize;
function resize() {
    canvas.width = window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth;
    canvas.height = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight;
}
let RAF = (function() {
    return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function(callback) {
        window.setTimeout(callback, 1000 / 60);
    };
})();
// 鼠标活动时，获取鼠标坐标
let ware = {x: null, y: null, max: 20000};
window.onmousemove = function(e) {
    e = e || window.event;
    ware.x = e.clientX;
    ware.y = e.clientY;
};
window.onmouseout = function(e) {
    ware.x = null;
    ware.y = null;
};
// 添加粒子
// x，y为粒子坐标，xa, ya为粒子xy轴加速度，max为连线的最大距离
let dots = [];
for (let i = 0; i <300; i++) {
    let x = Math.random() * canvas.width;
    let y = Math.random() * canvas.height;
    let xa = Math.random() * 2 - 1;
    let ya = Math.random() * 2 - 1;
    dots.push({
        x: x,
        y: y,
        xa: xa,
        ya: ya,
        max: 6000
    })
}
// 延迟100秒开始执行动画，如果立即执行有时位置计算会出错
setTimeout(function() {
    animate();
}, 100);
// 每一帧循环的逻辑
function animate() {
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    // 将鼠标坐标添加进去，产生一个用于比对距离的点数组
    let ndots = [ware].concat(dots);
    dots.forEach(function(dot) {
        // 粒子位移
        dot.x += dot.xa;
        dot.y += dot.ya;
        // 遇到边界将加速度反向
        dot.xa *= (dot.x > canvas.width || dot.x < 0) ? -1 : 1;
        dot.ya *= (dot.y > canvas.height || dot.y < 0) ? -1 : 1;
        // 绘制点
        ctx.fillRect(dot.x - 0.5, dot.y - 0.5, 1, 1);
        // 循环比对粒子间的距离
        for (let i = 0; i < ndots.length; i++) {
            let d2 = ndots[i];
            if (dot === d2 || d2.x === null || d2.y === null) continue;
            let xc = dot.x - d2.x;
            let yc = dot.y - d2.y;
            // 两个粒子之间的距离
            let dis = xc * xc + yc * yc;
            // 距离比
            let ratio;
            // 如果两个粒子之间的距离小于粒子对象的max值，则在两个粒子间画线
            if (dis < d2.max) {
                // 如果是鼠标，则让粒子向鼠标的位置移动
                if (d2 === ware && dis > (d2.max / 2)) {
                    dot.x -= xc * 0.03;
                    dot.y -= yc * 0.03;
                }
                // 计算距离比
                ratio = (d2.max - dis) / d2.max;
                // 画线
                ctx.beginPath();
                ctx.lineWidth = ratio / 2;
                ctx.strokeStyle = 'rgba(0,0,0,' + (ratio + 0.2) + ')';
                ctx.moveTo(dot.x, dot.y);
                ctx.lineTo(d2.x, d2.y);
                ctx.stroke();
            }
        }
        // 将已经计算过的粒子从数组中删除
        ndots.splice(ndots.indexOf(dot), 1);
    });
    RAF(animate);
}